Effects of microplastic and microglass particles on soil microbial community structure in an arable soil (Chernozem)

Abstract. Since decades, microplastics and microglass enter aquatic and terrestrial environments. The complexity of the environmental impact is difficult to capture and consequences on ecosystem components e.g. such as soil microorganisms are virtually unknown. Addressing this issue, we performed an incubation experiment by adding 1 % of five different types of impurities (≤ 100 µm) to an agricultural used soil (Chernozem). Four microplastic types (polypropylene (PP), low density polyethylene (LD-PE), polystyrene (PS) and polyamide12 (PA12)) and microglass were used as treatment variants. After 80 days of incubation at 20 °C, we examined soil microbial community structure by using phospholipid fatty acids (PLFA) as markers for bacteria, fungi and protozoa. The results showed that soil microorganisms were not significantly affected by the presence of microplastic and microglass. However, PLFAs tend to increase in LD-PE (27 %), PP (18 %) and microglass (11 %) treated soil in comparison with untreated soil, whereas PLFAs in PA12 (32 %) and PS (11 %) treated soil decreased. Interestingly, the comparison of PLFA contents between microplastic types revealed significant differences of PA12 (−87 %) and PS (−42 %) compared to LD-PE. Furthermore, bacterial PLFAs showed a much higher variability after microplastic incubation whereby fungi seem to be more unaffected after 80 days of incubation. Same for protozoa, which were more or less unaffected by microplastic treatment showing only minor reduction of the PLFA contents compared to control. In contrast, microglass has obviously an inhibiting effect on protozoa because PLFAs were under the limit of determination. Our study provides hints, that microplastics have, depending on type, contrary effects on soil microbiology and microglass seems to be highly toxic for protozoa.